Abstract:
Based on the hourly precipitation data of 28 national stations from 2005 to 2019, the spatial-temporal distribution characteristics of short-time heavy rainfall over Longitudinal valley area in Hengduan Mountain have been studied. The results show that:(1)Annual precipitation decreases from west to east in Longitudinal valley area, while percentage of short-time heavy precipitation in annual precipitation increases from northwest to southeast. The spatial distribution of short-term heavy rainfall frequency is extremely uneven, ranging from 0.1 to 6.7 times/a,and the upper part is less,but the downstream of Nu river and Jinsha river are maximums.(2)Annual short-time heavy rainfall increases by 0.022 times/a. Seasonal variation of frequency is obvious. The monthly variation peak appears in July-August,two maximum centers in the lower part are prominent from June to September. Four peaks of pentad variation are outstanding (36th, 39-44th, 47th, 51st pentad), and the decreasing trend after the 51st pentad is stronger than the increasing trend before 36th pentad. Spatial distribution shows that the peak frequency arrival time in northeast is earlier than that in southwest. (3)Main peak on diurnal variation of frequency occurs at wee hours, second peak at late in the afternoon. The spatial distribution of frequency increases from north to south and southeast,and that the two large value centers in the lower reaches of Nujiang and Jinsha river are obvious at midnight,wee hours and early morning,while the frequency shows little spatial distribution difference between afternoon and evening.Diurnal variation range of frequency is large in the middle and upper part of Longitudinal valley area, and the western part of that has short-time heavy rainfall at night, while the eastern part at afternoon and evening. Diurnal variation range of frequency is less in the lower part area, which occurs possibly in the afternoon, evening and night. These characteristics of short-time heavy rainfall are closely related to the terrain elevation of Longitudinal valley area in Hengduan Mountain and the South Asian Monsoon’s activity.